My son is 22 lbs and I love his Sandy's but they really don't fit great under his BSWW- especially since there are no gussets to tuck into. There's always a piece of the fluffy leg holes sticking out even though I try to fold them under and toward him.

I love the snap Bummis with Sandy's. My son is bigger so we were using Toddlease (toddler sized Sandy's) with XL Bummis snap wraps. The only reason we don't use them now is that my son outgrew them but it was a great combo that I'd recommend).